Double-layer capacitors, which are also known as ultracapacitors and supercapacitors, are now capable of being produced as individual capacitor cells that can store hundreds and thousands of farads. Due in part to their large capacitance, double-layer capacitors are capable of supplying or accepting large currents. However, single double-layer capacitor cells are limited by physics and chemistry to a maximum operating voltage of about 4 volts, and nominally to about between 2.5 to 3 volts. As higher capacitance capacitors are configured for use in increasingly higher voltage applications, even higher currents may be generated during charge and discharge of the capacitors. Use of double layer capacitors in high current applications will need to address increases in heat.